Update polyglot article

[sebastienros]

The PR #277 introduce a new article about polyglot support.

This article needs to be updated:

• Suggest aspire new -l typescript --name my-apphost after the init sample
• After adding integrations, show the changes to add a usage of these integrations and then how to run the apphost (aspire run). Only use the postgres and azure storage integrations though.
• add another paragraph showing how to also add a javascript application, just the apphost changes, the application is for the user to create. It may require the correct integration to be added though.
• use $HOME for powershell commands to represent the home dir
• Important: Remove all other languages that are not TypeScript. We only want to cover this language for now.